Ammonia washing method desulfurization process

1. Working principle

Ammonia desulfurization technology (abbreviated as ammonia desulfurization) is similar to gypsum desulfurization, and it is an advanced, efficient and economical desulfurization system. In the absorption tower, after the absorption liquid contacts the flue gas, the sulfur dioxide in the flue gas combines with the solution (NH4)2SO3, NH4HSO3, and finally forms ammonium sulfate crystals.

2. The reaction process.

(1) Absorption.

SO2+(NH4)2SO3+H2O→2NH4HSO3.

(2) Neutralization.

NH3+NH4HSO3→(NH4)2SO3.

(3) Oxidation.

2(NH4)SO3+O2→2(NH4)2SO4.

3. System construction.

It is mainly composed of flue gas system, absorption tower system, absorbent system, concentration tower system, by-product treatment system, waste water treatment system, public system, electrical control system, etc.

4. Process flow.

Boiler room/kiln → oil suction → fan → concentration tower → oil suction → boiler room.

After the boiler and kiln dust is removed, it enters the concentration tower and absorption tower through the fan. The absorption tower is a countercurrent shower tower structure, which integrates adsorption and oxidation. The upper part is the absorption zone, and the lower part is the oxidation zone. The spray smoke is in reverse contact with the circulating slurry in the absorption tower.

The system generally installs 2 to 3 slurry circulation pumps, each of which corresponds to a spray layer. Stop when the unit is running or under load. At this time, the system still maintains a high liquid-to-gas ratio to achieve the necessary desulfurization effect. The upper part of the absorption zone is equipped with a secondary demister, and the free moisture in the flue gas at the outlet of the demister is less than 75 mg per cubic meter.

The slurry that adsorbs carbon dioxide enters the circulating oxidation zone. Ammonium sulfite is oxidized into ammonium sulfate crystals by expanding air in the circulating oxidation zone. At the same time, the absorbent preparation system provides fresh ammonia gas or liquid ammonia for the absorption oxidation system, supplements the consumed ammonia gas, and keeps the absorption solution at a certain pH. When the concentration of the reaction product solution reaches a certain level, it is first discharged into the concentration tower in front of the absorption tower, and then enters the desulfurization by-product system after concentration. After dehydration, ammonium sulfate crystals are formed, further dried, and packaged for commercial use.

5. Process characteristics.

1. High desulfurization efficiency, which can guarantee more than 98%;

2. Low system energy consumption;

3. Strong adaptability to changes in coal types and load changes, suitable for high-sulfur coal;

4. The economic benefits of by-product recovery are high;

5. Obvious denitration effect;

6. Scope of application.

Flue gas desulfurization mainly includes coal-fired power generation boilers, thermal power plant boilers, central heating boilers, sintering machines, ball kilns, coke ovens, and glass kilns.